<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>固定定位</title>
    <style>
        div{
            height:200px;
            width:200px;
            background: #54b9e2;
            position:fixed;
            right:30px;
            bottom:30px;
        }
    </style>
</head>
<body>
    <div>我是小广告</div>
</body>
</html>